1. Field of the Invention
The present invention relates to a sheet material information detection device that detects information about the characteristics of a sheet material such as a sheet material used as a medium for image formation. The present invention also relates to a sheet material processing apparatus that controls the processing of a sheet material in accordance with that detected information.
2. Description of the Related Art
In recent years, there has been an increasing need for improved quality (improved image quality, increased processing speed, etc.) of image forming apparatuses (electro photographic apparatuses such as laser beam printers and copiers, ink jet printers, etc.). Meanwhile, the types of sheet materials used have become more diversified according to the requirements of users who use such apparatuses and the environment in which such apparatuses are used. Therefore, sheet material processing apparatuses need to cope with diverse types of sheet materials.
Japanese Patent Laid-Open No. 10-152245 discloses a system that determines characteristics such as type and physical properties of a sheet material by measuring the behavior of members that are brought into contact with the sheet material passing there between and regulates the settings of a printer in accordance with the determined type and characteristics. Japanese Patent Laid-Open No. 2002-310866 discloses a sheet material information detection device that applies an impact force to a sheet material and measures the physical properties of the sheet material in accordance with the compressibility of the sheet material.
A sheet material processing apparatus often performs a plurality of steps including a step for conveying a sheet material and a step for fixing colorants. In the step for conveying a sheet material, for example, a sheet material is conveyed by using a pair of rollers or the like. In this step, the sheet material is subjected to two concurrent loads: a load in the compressing direction applied when the sheet material is nipped between the rollers, and a load in the conveying direction applied when the rollers nipping the sheet material there between rotate. In order to optimally control the step for conveying a sheet material, the following pieces of information need to be obtained simultaneously: information about characteristics of the sheet material in the compressing direction (e.g. information about thickness, compressibility, and the like in a direction perpendicular to the sheet material surface), and information about characteristics of the sheet material in the conveying direction (e.g. information about coefficient of friction, presence of bumps/recesses, and the like in a direction parallel to the sheet material surface). Simultaneously obtaining information about characteristics of the sheet material in different directions is also needed for controlling toner transfer from a transfer roller performed in electro photographic apparatuses and for controlling a heating/compressing process performed in fixing devices, although the types of necessary information vary. Therefore, in order to optimally control a sheet material processing apparatus, it is necessary to simultaneously obtain information about characteristics of a sheet material in different directions including at least a direction perpendicular to the surface of the sheet material.
However, in the above-described known system and device, which can detect sheet material information in one direction, it is difficult to detect sheet material information in different directions.